Piston rod seal

ABSTRACT

A controllable coolant pump of internal combustion engines, including a pump housing, a drivable pump shaft rotatably in the pump housing, an impeller fixed on a free end of the pump shaft, and a pressure-difference-driven actuator to drive at least one piston rod guided in a piston rod bore of the pump housing, which includes a control spool at the impeller-side end of the piston rod, and which is guided in the piston rod bore by a guide bushing which is a portion of a sealing device which seals off a pump space carrying coolant with respect to the pressure-difference-driven actuator. The sealing device includes two seals which are spaced apart from one another, are on one end of the guide bushing, and include a static sealing area surrounding the guide bushing on the circumferential side and a dynamic sealing area adjoining the static sealing area.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of PCT Application No. PCT/EP2020/070670, filed on Jul. 22, 2020, and with priority under 35 U.S.C. § 119(a) and 35 U.S.C. § 365(b) being claimed from German Application No. 10 2019 122 718.6, filed on Aug. 23, 2019, the entire disclosures of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a controllable coolant pump of internal combustion engines.

BACKGROUND

Controllable coolant pumps have a control system for varying the cooling capacity. Such a control system is described in, for example, DE 10 2005 062 200 B3. A valve spool has an outer cylinder which variably covers the discharge area of the impeller of the coolant pump. The valve spool is arranged on several piston rods which are movably mounted in the pump housing. The position of the valve spool reflects the coolant flow and thus the cooling capacity. The piston rods are guided in a sealed piston guide in the pump housing. Sealing devices used for such a seal are known, for example, from the publication EP 2 722 567 A1. The sealing device has a bushing-shaped base body which serves as a guide for the piston rod. A seal is attached to one end of the base body in each case. The seals have dynamic sealing sections which are designed as sealing lips. A disadvantage of this sealing device is that pressure support is not effective at low pressure differences, and aged sealing components cause leaks to occur.

SUMMARY

Example embodiments of the present disclosure provide controllable coolant pumps each including a piston rod guide, which includes a sealing device that always ensures a reliable seal even under load.

An example embodiment of the present disclosure provides a controllable coolant pump of internal combustion engines including a pump housing, a drivable pump shaft rotatably mounted in the pump housing, an impeller fixed on a free end of the pump shaft, and a pressure-difference-driven actuator to drive at least one piston rod which is guided in a piston rod bore of the pump housing and includes a control spool held at the impeller-side end of the piston rod. The control spool variably covers an outflow region of the impeller, the piston rod being guided in the piston rod bore by a guide bushing which is a portion of a sealing device which seals off a pump chamber carrying the coolant from the pressure-differential-driven actuator, the sealing device including two seals which are spaced apart from one another, which are on one end of the guide bushing, and which include a static sealing area surrounding the guide bushing on a circumferential side and a dynamic sealing area adjoining the static sealing area, a first seal to seal off a pressure space of the pressure-difference-driven actuator at an end of the guide bushing remote from the impeller and a second seal to seal off the pump space carrying coolant at the end of the guide bushing adjacent the impeller. The dynamic sealing area of the first seal extends into the interior of the guide bushing from an end surface at the end remote from the impeller and is tapered inward into the guide bushing in the axial direction. The dynamic sealing area thus provides a reliable seal of the pressure chamber. In the event that coolant enters the space between the seals, the structure ensures that the first seal does not lift off the piston rod but remains sealingly adjacent to it, thus always providing a secure seal.

Preferably, the dynamic sealing area of the first seal is spaced from the inside of the guide bushing in the unloaded state.

If the piston rod tilts in the bore, a dynamic area of the first seal follows the movement without losing the radial circumferential contact, in particular line contact, with the piston rod. The structure of the first seal ensures that a reliable seal is maintained even if the piston rod tilts.

Preferably, an outer side of the static sealing area of the first seal is in sealing contact with an inner side of the piston rod bore.

In an example embodiment, the static sealing area of the first seal includes an annular protrusion in an area of the end surface of the sealing device, which is compressed during installation.

Preferably, the dynamic sealing area of the second seal extends from the end surface of the guide bushing adjacent the impeller into the pump chamber and lies outside the guide bushing.

It is advantageous if the dynamic sealing area of the second seal on the inside rests securely against the piston rod when installed.

Preferably, the outside of the static sealing area of the second seal is in sealing contact with the inside of the piston rod bore, and the dynamic sealing area adjoining the static sealing area is tapered on its outer side away from the guide bushing at its end on the impeller side to ensure that the second seal is always in radial circumferential contact with the piston rod, in particular with line contact.

Preferably, the dynamic sealing area of the second seal includes a sealing lip on the inside. An annular groove is provided concentrically with respect to the unloaded piston rod is between the conical region of the second seal and the sealing lip on the end surface, which annular groove permits movement in the radial direction of the sealing lip of the second seal and the conical region of the second seal independently of one another.

It is advantageous if the second seal is pushed onto the guide bushing and engages in an annular groove of the guide bushing to fix the position. The two seals are preferably rotationally symmetrical.

Preferably, a drainage outlet is between the two seals in the guide bushing.

The dynamic sealing areas are preferably sealing lips.

The seals preferably surround the guide bushing at least partially on the end surface.

Preferably, the guide bushing is made of a thermoplastic material. Preferably, the sealing device includes elastomer seals.

Furthermore, it is advantageous if the piston rod can be moved parallel to the pump shaft by the pressure difference driven actuator. The pressure difference driven actuator can be a pneumatic or hydraulic actuator. In an example embodiment of the present disclosure, the pressure difference driven actuator is a pneumatic drive. The vacuum chamber is preferably sealed by, among other things, a rolling diaphragm. When the vacuum chamber is evacuated, the diaphragm rolls out due to the pressure difference between the atmospheric pressure and the vacuum region and moves a piston slide in which the piston rods are suspended.

The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present disclosure is explained in more detail below with reference to the drawings. Similar or similarly acting components are designated in the figures with the same reference signs.

FIG. 1 shows a longitudinal section through a controllable coolant pump with a sealing device according to an example embodiment of the present disclosure.

FIG. 2 shows a detailed view of a sealing device according to an example embodiment of the present disclosure in longitudinal section.

FIG. 3 shows an enlarged view of a guide bushing of the sealing device of FIG. 2 in longitudinal section and in spatial representation.

FIG. 4 shows an enlarged view of a first seal of the sealing device of FIG. 2 in longitudinal section.

FIG. 5 shows an enlarged view of a second seal of the sealing device of FIG. 2 in longitudinal section.

DETAILED DESCRIPTION

FIG. 1 shows a controllable coolant pump 1 with a pump housing 2. The pump shaft 4, which is driven by a drive wheel not shown, is rotatably mounted in the pump housing 2 in a pump bearing 3. An impeller 5 is seated non-rotatably on the free, flow-side end of the pump shaft 4. The pump shaft 4 is surrounded by a mechanical seal 6 between the pump bearing 3 and the impeller 5. A pressure-actuated control spool 7 is arranged in the pump interior. The control spool 7 is pot-shaped with a central opening 8. It concentrically surrounds the pump shaft 4. It has an annular base 9 and a lateral surface 10 surrounding the base 9. Depending on the position of the control spool 7, the lateral surface 10 covers the outflow area 11 of the impeller 5. In the area of the base 9, the control spool 7 is firmly connected to preferably three guide rods 12. The guide rods 12 extend parallel to the pump shaft 4 and are evenly distributed over its circumference. The guide rods 12 are piston rods which are axially guided in piston rod bores 13 in the pump housing 2.

The piston rods 12 are driven by a pressure differential driven actuator, in this case a pneumatic actuator operating with negative pressure. The piston rod 12 is guided on the control spool side in a guide bushing 14 in the piston rod bore 13. The guide bushing 14 is part of a sealing device 15, each with two seals 16. The two seals 16 are each arranged at one end of the guide bushing 14. They are spatially separated from each other and do not influence each other. The seal far from the impeller seals the vacuum chamber of the pneumatic drive and the seal near the impeller seals the pump chamber carrying coolant.

A drainage outlet 17 arranged between the two seals 16 can discharge a coolant that has penetrated into the space between the two seals 16.

The piston rod 12 is held on the vacuum side in a piston slide 18. The piston slide 18 is arranged in a piston slide holder in a rolling diaphragm in a vacuum chamber 19 whose inner diameter is larger than that of the piston rod bore 13. The receptacles of the piston slide 18 are thus connected to each other via the continuous rolling diaphragm. The vacuum chamber is sealed by the rolling diaphragm, which also receives the piston slide. The vacuum area is sealed by axial compression of the rolling diaphragm in the housing and the seal 16 in contact with the piston rod. This area is connected to the vehicle's vacuum supply by a hose nozzle pressed into the housing. When the vacuum chamber is evacuated, the diaphragm rolls out due to the pressure difference between atmospheric pressure and the vacuum area, thus moving the piston slide in which the piston rods are suspended.

By the pneumatic drive, the control spool 7 can be moved between an open position and a closed position. In the open position shown in FIG. 1, the outflow area 11 of the impeller 5 is free and not covered by the control spool 7. In the closed position, however, the control spool completely covers the outflow area.

In order to reduce tilting of the piston rod 12 in the pump housing 2 and a load on the sealing device 15, a second guide 20 of the piston rod 12 in the pump housing 2 is provided. The second guide point 20 is formed by a through hole 21 between the piston slide holder and the piston rod bore 13. The through hole 21 has a clear width that is smaller than the clear width of the piston slider receptacle 19 and piston rod bore 13. The clear width of the through hole 21 is matched with some clearance to the outer diameter of the piston rod 12. The cylindrical portion of the through hole 21 is to be designed as small as possible so that the risk of jamming of the guide rod 12 in the through hole 21 is minimized. The piston rod 12 is thus guided only on the vacuum side on the pump housing 2 and in the area of the sealing device 15 by a guide bushing 14 in the pump housing 2. Due to the “two-point guide”, tilting of the piston rod 12 is only possible to a limited extent even when force is applied to the piston rod 12. The sealing device 15 will age over the life of the pump, which reduces its compensating capacity in the event of piston rod deflection. The two-point guide reduces the radial deflection of the piston rod, so that the compensating capacity of the sealing device 15 does not have to be so high.

FIGS. 2 to 5 show in detail a preferred sealing device 15. The guide bushing 14 has an interpenetrating opening 22, which has a continuously widening inner diameter. In the assembled state, the opening 22 is penetrated by the piston rod 12. In the area of the smallest inner diameter, the piston rod 12 is guided in the guide bushing 14. The guide bushing 14 is preferably injection molded from a thermoplastic. For demolding the finished plastic part from the injection mold, a demolding bevel (also called a lift-out bevel) is preferably provided in the inner diameter, which results in the piston rod 12 being guided only at the smallest diameter of the guide bushing 14.

The guide bushing 14 has two sections 23,24, each of which is designed to receive a seal 16. The two sections 23,24 are connected to each other by a central area 25, which is penetrated by at least one radial opening 26. In the illustrated example embodiment example, two radial openings 26 are provided in alignment with one another. The outer diameter of the guide bushing 14 in this central region 25 is significantly smaller than the inner diameter of the piston rod bore 13, so that a circumferential recess 27 is formed on the outside of the guide bushing 14. The radial openings 26 form an inner drainage outlet and the circumferential recess 27 an outer drainage outlet. A coolant that has entered the guide bushing 14 can be drained radially outwardly into the recess 27 through the radial openings 26 and discharged outwardly through the drainage outlet. Due to the circumferential recess 27, it is not necessary to pay attention to a positionally accurate installation position of the sealing device 15. In the axial direction, however, care must be taken to ensure exact positioning in order to form the leakage system with the circumferential recess 27 of the guide bushing 14 and the leakage drainage holes in the pump housing 2, otherwise the areas 23 and 24 will close off the leakage system of the pump.

The section 23 of the guide bush 14 close to the impeller has a circumferential groove 241, which is bounded in the axial direction respectively by two annular webs 242,243. The inner web 243 has an outer diameter which produces the interference fit in the housing by overlapping with the piston rod bore 13.

A pneumatic seal 234 is accommodated at the axial end 231 of the section 23 remote from the impeller for sealing with respect to the pressure differential-controlled actuator or the vacuum chamber. The seal 234, shown in detail in FIG. 4, has a static sealing area 235 which surrounds the guide bushing 14 circumferentially with the inner side and which is seated on the outer side of the guide bushing at the end 231. The outer side of this static sealing area 235 abuts the inner side of the piston rod bore 13. The static sealing area 235 surrounds the end surface of the end 231 of the guide bushing 14 remote from the impeller and thus completely covers it. The end surface formed in the installed position of the sealing device by the pneumatic seal 234 is in contact with a shoulder 28 of the piston rod bore 13 in the assembled state, which is formed by the narrowing to form the through hole 21. The radial overlap of the outer diameter of the pneumatic seal 234 with the piston rod bore ensures a static seal. It may also be provided that the pneumatic seal 234 has a circumferential bead, not shown, on the front face, which is axially compressed during assembly.

The static sealing section 235 of the pneumatic seal 234 merges into a dynamic sealing section 237, which is formed as a sealing lip. The sealing lip 237 extends inwardly into the guide bushing 14 in the axial direction, protruding inwardly from the inside of the guide bushing 14 in the radial direction, and is tapered inside the guide bushing 14 in the direction of the pump chamber while maintaining the same wall thickness. In other words, the taper is present on the inner side and the outer side of the sealing lip 237. When the piston rod 12 is mounted, the dynamic sealing section 237 is in sealing contact with the outside of the piston rod 12 under radial preload. The dynamic sealing section 237 is dimensioned in such a way that at least one third, in particular more than 40%, of the height, defined in the axial direction, of the section 23 of the guide bushing 14 remote from the impeller wheel and extending from the leakage groove 25 is covered in the interior.

On the side of the sealing device 15 facing the actuator, negative pressure prevails in the pump housing 2. In contrast, atmospheric pressure prevails between the seals 23,24. Due to the pressure difference, the sealing lip 237 nestles against the piston rod 12 on its inner side. In the event that cooling liquid enters the space between the seals 23,24 and the pressure on the dynamic sealing section 237 increases from the inside, the dynamic sealing section 237 is pressed against the piston rod 12 and the tightness is increased. It is thus possible to prevent the pneumatic sealing member 234 from leaking due to load.

A hydraulic seal 244 is received in the groove 241 of the section 24 of the sealing device 15 near the impeller for sealing against the pump chamber. The seal 244 shown in detail in FIG. 5 has a static sealing area 245 which surrounds the guide bushing 14 on the circumferential side and which engages in the annular groove 241. The outer side of the static sealing area 245 abuts the inner side of the piston rod bore 13. The static sealing area 245 at least partially surrounds the end surface of the guide bushing near the impeller and merges into a dynamic sealing area 246, which projects outwardly in the axial direction beyond the guide bushing 245. The dynamic sealing area 246 extends inward in the radial direction and is formed as a sealing lip. The sealing lip 247 extends from the end surface of the guide bushing 14 near the impeller into the pump chamber. The sealing lip 247 is conical and tapers away from the guide bushing 14. Its end near the impeller therefore fits tightly against the piston rod 12. The inner diameter of the sealing lip 247 in this area is selected so that the hydraulic seal 244 is securely in contact with the piston rod 12. The pump medium pressure on the hydraulic seal 244 presses the sealing lip 247 against the piston rod 12.

While example embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims. 

1-10. (canceled)
 11. A controllable coolant pump of internal combustion engines, the controllable coolant pump omprising: a pump housing; a drivable pump shaft rotatably mounted in the pump housing; an impeller non-rotatably fixed on a free end of the pump shaft; and a pressure-difference-driven actuator to drive at least one piston rod which is guided in a piston rod bore of the pump housing and including a control spool valve held at an impeller-side end of the piston rod; wherein the control spool is set up to variably cover an outflow region of the impeller; the piston rod is guided in the piston rod bore by a guide bushing which is a portion of a sealing device which seals off a pump chamber carrying coolant from the pressure-difference-driven actuator; the sealing device includes two seals which are each on one end of the guide bushing and which each include a static sealing area circumferentially surrounding the guide bushing and a dynamic sealing area adjoining the static sealing area, a first seal to seal a pressure chamber of the pressure-differential-driven actuator at an end of the guide bushing remote from the impeller, and a second seal to seal the pump chamber carrying coolant at the end of the guide bushing adjacent to the impeller; and the dynamic sealing area of the first seal extends into an interior of the guide bushing from an end surface at the end remote from the impeller, the dynamic sealing area of the first seal tapering inwards into the guide bushing in an axial direction.
 12. The controllable coolant pump according to claim 11, wherein the dynamic sealing area of the first seal is spaced from an inner side of the guide bushing in an unloaded state.
 13. The controllable coolant pump according to claim 11, wherein an outside of the static sealing area of the first seal sealingly abuts an inside of the piston rod bore.
 14. The controllable coolant pump according to claim 11, wherein the static sealing area of the first seal includes an annular protrusion adjacent to an end surface of the sealing device.
 15. The controllable coolant pump according to claim 11, wherein the dynamic sealing area of the second seal extends from an end surface of the guide bushing adjacent to the impeller into the pump chamber and lies outside the guide bushing.
 16. The controllable coolant pump according to claim 11, wherein an outer side of the static sealing area of the second seal bears against an inner side of the piston rod bore in a sealing manner, and the dynamic sealing area of the second seal tapers in a conical region on an outer side thereof away from the guide bush at an end thereof on an impeller side.
 17. The controllable coolant pump according to claim 11, wherein the second seal is slidable onto the guide bushing and engageable with at least one annular groove of the guide bushing to fix the position.
 18. The controllable coolant pump according to claim 11, wherein a drainage outlet is between the two seals in the guide bushing.
 19. The controllable coolant pump according to claim 11, wherein the dynamic sealing areas include sealing lips.
 20. The controllable coolant pump according to claim 11, wherein the seals at least partially surround the guide bushing on the end surface. 